I. Field
The present invention relates generally to communication, and more specifically to a method and apparatus for reducing delay or latency in accessing a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and so on. These systems may be multiple-access systems capable of supporting communication for multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, and Frequency Division Multiple Access (FDMA) systems.
A wireless device (e.g., a cellular phone) may actively exchange data with a base station for a voice or data call. At the start of the call, the wireless device may exchange signaling with the base station to receive a channel assignment, configure various parameters, and so on. Thereafter, the wireless device may exchange data with the base station using the assigned channels and configured parameters.
A wireless device may also be intermittently or sporadically active for a call. For example, the wireless device may have a push-to-talk (PTT) call with one or more other peer wireless devices. The wireless device may receive messages from the peer wireless devices and may also transmit messages to these peer wireless devices whenever initiated by a user at the wireless device. Data transmission and reception by the wireless device for the PTT call may be sporadic and may occur at any time. To conserve battery power and extend both standby time and talk time, the wireless device may power down as much circuitry as possible when not transmitting during the PTT call. If the user desires to send a message, then the wireless device would need to wake up and perform access procedures before the device can start transmitting. The delay incurred to perform the access procedures is called “access latency”. Reducing access latency is important in order to achieve a quick response to a user-initiated transmission. Minimal access latency can enhance user experience and is highly desirable for PTT and other time sensitive applications.
There is therefore a need in the art for techniques to reduce access latency in a wireless communication system.